2g38

A PE/PPE Protein Complex from Mycobacterium tuberculosis
The heterodimeric PE/PPE protein complex from M. tuberculosis is composed of a 99 amino acid PE protein protein (Rv2431c, shown in RED) and a 194 amino acid PPE protein (Rv2430c, shown in BLUE), that are encoded next to each other on the M. tuberculosis genome (suggestive of a potential operon). These proteins represent two of the largest protein families in the M. tuberculosis genome. The PE and PPE proteins form an elongated helical structure, reminiscent of a four-helix bundle, which can be best viewed down the axis. The protein interaction interface between the two proteins is lined with hydrophobic residues, contributing to the stability of the protein complex. Click here to view a SpaceFill representation.

About this Structure
2G38 is a Protein complex structure of sequences from Mycobacterium tuberculosis h37rv. Full crystallographic information is available from OCA.



Above depicts the crystal structure of the M.tb. PE/PPE protein complex (Adapted from Strong et al. PNAS 103: 8060–8065 ). (a) Surface representation of the PE/PPE protein complex. The PE protein Rv2431c is shown in red, and the PPE protein Rv2430c is in blue. (b) The PE/PPE protein complex viewed down its longitudinal axis. (c) Ribbon diagram of the PE/PPE protein complex. The complex is composed of seven α-helices. Two α-helices of the PE protein interact with two helices of the PPE protein to form a four-helix bundle. Regions of high sequence conservation are indicated by arrows and discussed in the text. (d) Interface hydrophobicity of the PPE and PE proteins. The hydrophobicity of the interaction interface between the PPE and PE protein is color-coded: the most apolar regions are indicated in red, orange, and yellow, and the most polar regions are indicated in blue. Notice the extensive apolar regions that are shielded from solvent as the complex forms. (Text and Figure adapted from Strong et al. Proc Natl Acad Sci U S A. 103: 8060–8065 (2006), Figure 3).



Interaction interface of the PE/PPE protein complex. (a) Two helices of the PE protein, α1 and α2, interact with two helices of the PPE protein, α2 and α3, to form a four-helix bundle. The four-helix-bundle is largely stabilized by hydrophobic interactions among apolar side chains, as seen in the core of the complex. In contrast, the outer surface is coated with polar residues. (b) The PE/PPE complex as viewed down the longitudinal axis (Text and Figure adapted from Strong et al. Proc Natl Acad Sci U S A. 103: 8060–8065 (2006), Figure 4).

Reference
Toward the structural genomics of complexes: crystal structure of a PE/PPE protein complex from Mycobacterium tuberculosis., Strong M, Sawaya MR, Wang S, Phillips M, Cascio D, Eisenberg D, Proc Natl Acad Sci U S A. 2006 May 23;103(21):8060-5. Epub 2006 May 11. PMID:16690741